Thermoresponsive restraining device



Jan. 17, 1933. w RQESSNER 1,894,425

THERMORESPONSIVE RESTRAINING DEVICE Filed March '7, 1952 ZflZZimm foam n67:

Patented Jan. 17, 1933 WILLIAM L. nonsense,

PATENT OFFICE,

or DENVER, COLORADO THERMORESPONSIVE RESTRAINING DEVICE Application filed March 7, 1932. Serial No. 597,154.

This invention relates to improvements in restraining elements for thermo responsive devices andhas reference more particularly to an improvement in the fusible link described and claimed in Letters Patent No. 1,875,661 granted to me onSeptember 6, 1932. For protection against fire, it is customary to provide different forms of fire extinguishing apparatus which are held in inoperative position by means of a fusible element. This element is usually formed'in part by a readily fusible solder that will melt at a comparatively lowtemperature and which is therefore adapted to release the fire extinguishing apparatus when the temperature reaches this point. It is also quite customaryto'provide buildings with fire partitions and fire doors and to hold these doors normally open by means of fusible links of the type referred to. Experience has shown that the usual form of fusible link employed in fire protective apparatus is not absolutely reliable for the reason that the solder onwhich it depends for its effectiveness is subjected to tension or to tortional strains and since the particular alloy of which this fusible solder is made has a comparatively small tensile strength, re-

straining devices of which it forms apart very frequently fail and release the fire extinguishing apparatus, even at times when the temperature, is normal or below normal.

It is the object of this invention to produce a thermo responsive restraining device that shall be so constructed that the fusible solder, instead of being subjected to tension or torsional; strains, will be subjected to compression mainly and since the alloy forming the fusible solder has comparatively large r esistance against compression, the danger of the restraining element failing-below. the temperature for which it is intended is greatly decreased and almost entirely removed.

In the application above identified, I have shownand described a restraining devicein which the readily fusible solder is subjected mainly tocompressive strains and this has proved very satisfactory in operation. It has been found, however, that where these restraining devices are employed for the purpose of resisting a very strong force provided by a strong spring or a heavy weight, that the severe compressive strains to which the solder is subjected will sometimes cause it to flow very slowly and therefore if the forces are not properly proportioned, the fusible element will change its shape gradually and will therefore release the apparatus, regardless of temperature conditions.

It is the object of this invention to produce a restraining device of the type indicated which shall be so constructed that the compressive strains, instead of being resisted entirely by the fusible solder,'will be resisted almost exclusively by a metal plug which may be made from copper, steel or any other suitable metal that is capable of resisting heavy compressive strains and which is held in position by means of readily fusible solder.

The above and other objects that may be come apparent as this description proceeds are attained by means of a construction and by an arrangement of parts that will now be described in detail, and for this purpose reference will be had to the accompanying drawing in which the invention has'been illustrated in a variety of forms and in which:

Fig. 1 is a plan View showing one of the improved restraining devices in operative position;

' Fig. 2 is a diagramshowing the relationship of the different forces to which the fusible material is subjected;

Fig. 3 is a section taken on line33, Fig. 1; v Fig. 4 is a side elevation showing one embodiment of the invention; I

Fig. 5 is a side elevation showing a form of restraining device similar to that illus trated in Fig. 1; 1 i v Fig. 6 shows a device similar to that illustrated in Fig. 5, but in which the ends 26 are curved so as to. form a chamber for the solder;

Fig. 7 is a modification of the device illustrated in Fig. 6;

Fig. 8 is aview showing another modified form;

Fig. 9 shows a still further modification;

and

' Fig. 10 shows a form suitable for use where very heavy strains must be resisted.

In Fig. 1 the typical arrangement of the different elements that cooperate with my improvedrestraining device has been illustrated and in this view reference numeral represents a stationary support to which one end of a spring 21 is secured. A movable plate 22 is provided with an opening 23 through which my improved restraining device extends. The restrammg devlce which has been illustrated in Fig. '1 is formed from asingle strip of metal, such, for example, as a brass strip 24. This strip is bent double and is provided at one end with aloop 25 with which one end of the spring is connected.

: 5 The two sides ofthe metal strip are parallel 2 of the spring 21, a plug 27 of copper or steel,

or anyother suitable material is placed in the apexof the angle between the two inclined sides and this plug is held in place by means of readily fusible solder 28. The pur- 4e P se 'ofthe plug 27 is to resist the compressive strains produced by the spring and the fusible solder merely serves to hold the plug in place. I

By. referring to Fig. 2 it will be seen that the force P produced by the spring or other equivalent means, is transmitted through the sides 24 of the link and is resisted by the plate 22. Since there are two inclinedsides which resist the action of the force equally,

5 then each side 26 will resist a force equal to one-halfP." -'This force can be divided into twocomponents, one of which is parallel with the plate 22 and the other of which is perpendicular to the side 26. These forces have been designated respectively as a and b. The value of these forces depend on the angle at which the side is inclined and this'has been indicated by the letter w. It will now be seen that the force a varies inversely as the tangent of the angle w and similarly force I) varies inversely as the sine of the angle to and directly as the force F. Since the value of the I tangent. varies from zero to infinity, the value of a can be made of any desired amount betweenthe limits of infinity and zero, while the value of the force I) can be varied from infinity to P.

From the above explanation, it will be seen that the fusible solder 28 that separates the sides 26 can be subjected to any desired pressure and when the angle w is very small, this pressure is very large in proportion to the tension exerted by the spring and as aboveexplained, it is possible to make this pressure so large that the solder will be forced sidewise so as to let the sides 22. approach each other sufficiently to release the mechanism.

In Fig. 1, as abovementioned, a plug 29 has been inserted at the apex of the angle to resist the forces, and therefore as long as the force is not sufficient to crush the plug or overcome the adhesion of the solder, the ends 26 can not be pulled through the opening.

In Fig.4 a modified form has been shown in which several plugs like those designated by29 .in Fig, 1 can be used. In accordance with Fig. 4, one of these plugs is located at the vertex of the angle, or the plugs may be grouped together without any definite relationship tov the sides 26. When theembodiment shown in Fig. 4 is used, the solderbetween thedifferent plugs is so thin that it will not flow except when subjected to very great stresses. In Fig. 5 a modificationxhasjbeen shown in which the several plugs shown in Fig. 4 have been replaced by a single tube 29 and this is also true of the embodiment shown in Fig. 6 which, in addition, has'the sides curved inwardly as shown for the purpose of facilitating the introduction of L the "solder.

Referring now to Figs. 4, 9. and 10, attentionis called to the fact'that in, addition to the plug 29, a numberof metal particles are embedded in the solder. It is well known that if a lump of plastic material such as gum or putty or soft metal such as lead or an alloy of considerable thicknessis put'under pressure, it will flow quite readily in a. direction transverse to the line of pressure. As the thickness of the'layer decreases the pressure i required to produce the same amount of flow must be increased and when the layer or layers become very thin, it requires very large pressure to produce any flow. By embedding a large number of metal particles in the solder, greater force can be resisted than if only a single plug" were used.

In Figs. 6,7, 8, 9 and 10, a. hollow or tubular member 29 is embodied in the solder. principal advantage of ahollow member over The a solid one is that the inside is subjected to the temperature prevailing about theout- .side of the solder and it will therefore release quicker and move nearly at the predeterminedtemperaturefl f V Due to the fact that the sides 26fareinclined asshown in Fig. 2,;there is, of course,

a force that tends to forcethe solder out and this is resisted by the adhesion of the solderto' the sides o'f'member's 26, and also by friction.

It is obvious that if angle W were less than i the angle of repose the solder could be laid loosely in place and would not move until it fused.

Fig. 7 shows a slightly modified form of the construction shown in Fig. 6 and differs from i the latter in this, that the ends 26, instead of being curved gradually, are bent about lines 30 into parallel overlapping relation.

It will be seen from the above that this invention in its broadest aspect comprises the introduction into the solder of a plug or other metal member that has greater resistance to compression than the solder itself and this,

by being placed in the apex of the angle as by this simple expedient the link can be constructed so as to withstand any reasonable amount of pressure. The plurality of plugs 29 shown in Fig. 4: serve to subdivide the solder and to some extent prevent it from flowing.

In the modification shown in Fig. 10, the ends 26 are longer than in Fig. 4, for example, and have their upper ends 26a inclined inwardly so as to form a diamond shaped cavity. Located within this cavity is a short tubular member 29 and if desired two smaller tubular members 29a may be placed in the apexes'of the angles formed by the sides 26 and 260,. A reenforcing member formed from a strip of material 42bent into diamond shape so as to fit the outside of the sides 26 and 26a enclose the latter and the free ends of this strip may be extended into the opening 23 in plate 22. A device constructed in accordance with Fig. 10 is especially suitable where very large forces are to be re-' sisted and is therefore intended more particularly for use with fire doors and similar devices, although it can be used any place where a thermo responsive releasing mechanism is desired.

From the above description it will be seen that by the simple expedient of introducing into the solder plug some solid matter oifering greater resistance tothe compressive strains than the solder itself, a restraining device can be constructed that will resist greater forces than if the sides 26 were separated by solder alone and since it is very important that devices of this type shall be inoperative until the temperature reaches a predetermined value it is essential that some means be provided for preventing the solder from slowly flowing transversely in the manner above indicated.

Having described the invention what is claimed as new is:

1. A restraining device for a thermo-re} sponsive mechanism comprising a member having two' substantially parallel flexible arms, the ends of the arms being spread apart and outwardly inclined, the adjacent surfaces of the inclined arms being connected by means of a spacer formed from readily fusible solder in which'is embedded a metal member of higher fusing point and greater compressive strength, said last named member being hollow whereby heated airwill have access to the interior'there'of.

2. A restrainingdevice for a thermomesponsive mechanism comprising a member having two substantially parallel flexible arms, the ends of the arms being spread apart and outwardly inclined, the adjacent surfaces of the inclined arms being connected by means of a spacer formed from readily.

fusible solder in which is embedded a tubular metal member of higher fusing point and greater compressive strength, and a member of higher fusing point than the solder connecting' the divergent ends and secured to them by easily fusible solder to entirely enclose the space and form .a reenforcing means.

3. A restraining device for a thermo-responsive' mechanism comprising a member having two substantially parallel flexible arms, the ends of the arms being spread apart and outwardly inclined, a hollow metal plug located in the apex of the angle formed by the two sides, easily fusible solder associated with the plug and the sides for holding the plug in place until the temperature reaches a predetermined value, and a removable reenforclng member of metal of high fusing pomt extending across the outer ends of the outwardly divergent arms and attached to them by easily fusible solder.

4. heat responsive restraining element comprismg, a tension member having one end formed from two outwardly inclined portions that are separated by means of readily i fusible solder, a hollow metal member of greater compressive strength and higher fusing point extending between the inclined ends and secured to the latter by the fusible fusible solder, and a separate member of higher fusing point than the solder connecting the divergent ends and secured to them by easily fusible solder to entirely enclose the space and form a reenforcing means.

A restraining device for a thermo-re-i sponsive mechanism comprising a member 7 having two substantially. parallel .flexible arms,-the ends of the arms being spread apart and outwardly inclined, the adjacent surfaces of the inclined arms being connected by means of a spacer formed from readily fusible solder in which is embedded a metal member of higher fusing point and greater V compressive strength, and a separate member i= ofhigher fusing point than the solder connecting the divergent ends and secured to them by easily fusible solder to entirely enclose the space and form a reenforcing means. In testimony whereof I affix my signature. a WILLIAM L. ROESSNER. 

